Recording and measuring instrument



March 6, 1956 J. E. BEVINS ETAL 2,737,433

RECORDING AND MEASURING INSTRUMENT Original Filed April 16, 1945 10Sheets-Sheet l JGJIZBSE. Ben/ Robert WHyde.

ATmRNEY March 6, 1956 J. E. BEVINS ET AL 2,737,433

RECORDING AND MEASURING INSTRUMENT Original Filed April 16, 1945 10Sheets-Sheet 2 Q VENTORS G .s E. Bevilus BY Rabat W/{ da fi TTRN EYMarch 6, 1956 J. E. BEVINS ETAL RECORDING AND MEASURING INSTRUMENT 10Sheets-Sheet 5 Original Filed April 16. 1945 March 1956 J. E. BEVINSETAL 2,737,433

RECORDING AND MEASURING INSTRUMENT Original Filed April 16, 1945 10Sheets-Sheet 4 R GHT 5/05 March 6, 1956 J. E. BEVINS ET AL RECORDING ANDMEASURING INSTRUMENT Original Filed April 16, 1945 FL'O. 6. P

10 Sheets-Sheet 5 Unveni'ors James E. Bevins Robert w lg de A T TORNEMarch 6, 1956 J. E. BEVINS ET AL RECORDING AND MEASURING INSTRUMENTOriginal Filed April 16, 1945 10 Sheets-Sheet 5 (DRIVEN BY MOTOR ATLOWSPEED) (DRIVES THE ESCH PEMENTf VEN BY MOTOR AT HIGHSPEED) NBRAKEUnvenio r5 Jculzes E. Bevilzs Robert W lfyde ATTORNEY March 6, 1956 J.E. BEVINS ET AL 2,737,433

RECORDING AND MEASURING INSTRUMENT Original Filed April 16, 1945 10Sheets-Sheet '7 96 (apes/arcs BRAKE) (DRIVES r145 Jnveni'or ESCAPE/MENUJanles E Bevilzs 97 Robert (DRIVEN er MOTOE) ATTORNEY.

March 6, 1956 J. E. BEVINS ET AL RECORDING AND MEASURLNG INSTRUMENT 10Sheets-Sheet 8 Original Filed April 16. 1945 Unven tors James E.Bevi1zsRobert W March 1956 J. E. BEVINS ET AL 2,737,433

RECORDING AND MEASURING INSTRUMENT Original Filed April 16, 1945 10Sheets-Sheet 9 Jnveni'or; James E Bev jas Robe/'1' A TTORNEY March 6,1956 J. E. BEVlNS ET AL RECORDING AND MEASURING INSTRUMENT 1OSheets-Sheet 10 Original Filed April 16. 1945 Urweni'ors JculcesE.Bev,z'a5

Robert W/lyde ATTORNEY United States Patent 2,737,433 RECORDING ANDMEASURING INSTRUMENT James E. Eevins, Ramsey, and Robert W. Hyde,Englawood, N. J., assignors to Bendix Aviation Corporation, Teterboro,N. J., a corporation of Delaware Original application April 16, 1M5,Serial No. 588,600. Divided and this appiication March 13, 1950, SerialN 0. 149,926

4 Claims. (Cl. 346-49) This invention relates generally to recordingand/ or indicating instruments and more particularly to a novel combinedinstrument adapted for permanently recording with respect to time andfor simultaneously indicating the instantaneous values of variousfunctions or conditions encountered during craft flight such as, forexample, airspeed, pressure, humidity, temperature, etc.

An object of the present invention is to provide an instrument of theforegoing character in which each of the functions being considered ismeasured at a distant point by an electrical transmitter which isconnected to a related electrical repeater at the instrument, therepeater actuating a marker pin relative to a recording chart as well asan index relative to a related graduated scale in correspondence withthe value of the conditions being measured.

A further object is to provide a high speed and light weight recorder ofa plurality of variable functions such as, for example, airspeed,pressure, humidity and temperature.

Still another object is to provide novel means for converting angularmotion of a self-synchronous repeater into linear motion of a markingand/ or indicating index with a minimum of friction and without the useof amplifiers or servo systems.

A further object is to provide a novel combined indicator and recorderof the values of a number of variables having continuously readableindications relative to graduated scales and with the recorded valuesfor a pre-selected period of time visible on the chart from the exteriorof the instrument, a cover having a window therein being provided forthe instrument, the windowbeingarranged over the chart and scales.

This is a division of patent application Serial No. 588,600, filed April16, 1945, now issued as PatentNo. 2,551,866 on May 18, 1951.

The above and other objects and advantages of the invention will appearmore fully hereinafter from a consideration of the detailed descriptionwhich follows taken together with the accompanying drawings. It is to beexpressly understood, however, that the drawings are for the purpose ofillustration and description only and are not designed as a definitionof the limits of the invention.

In the drawings wherein like reference characters refer to like partsthroughout-the several views:

Figure 1 is a perspective view, generally from the front, of theinstrument with the cover on;

Figure 2 is a front elevation of the instrument with the cover removed;

Figure 3 is a generally corresponding plan View, partially in section,showing the ribbon handling mechanism;

Figure 4 is partial elevation, partially in section, of the righthandend of the recorder showing the operating motor and its regulator, theplaten-operating mechanism and its lock-out detent, and the ribbonmechanism.

Figure 5 is an elevation of the lefthand end of the recorder, also withthe cover removed.

Figure 6 is a sectional elevation,- the section beingv taken 2,737,433Patented Mar. 6, 1956 along line;6-6 in Figure. 2, showing the charthandling mechanism.

Figure-7 is a partial rear elevation showing the location of the re-rolldevice and of the chassis for the electrical centering of the synchroswhen starting up;

Figure 8 is a somewhat diagrammatic View of the speed control for themotor drive taken, generally looking toward the lefthand end oftheinstrument, with the synchro unit removed;

Figure 9 is a sectional mechanism diagram of the control of Figure 8,taken along lines 9-9;

Figure 10 is'a sectional view of the screwrdifferential mechanism whichactuates the control of Figures 8 and 9, being taken along line 10-10 ofFigure 8;

Figures 11 and 12 are respectively an end elevation and section of theescapement mechanism, Figure 12 being taken along line 12-12 in Figure11.

Figure 13 is a perspective view of the ribbon and platen drive with theindicating mechanism removed to show the ribbon drive;

Figure 14 is a plan view, partially in section, of the platen and aportion of its actuating means;

Figure 15 is a section of an irreversible clutch in the chart-drivegearing;

The device disclosed, by way of example, continuouslyindicatesthe-values of fourvariables, including the velocity of a craftcarrying the instrument, by the position of indices moved longitudinallyalong their respective scales. It also recordseach of these values in adifferent color on a, standard strip chart which is ten inches widev onthe graduated portion and. which moves at twelveinches per hour. It alsorecordsastandard width by marginal marks so as to indicate any errorsdueto changes in width of the chart, such as, are. due to variations ofrelative humidity and temperature of the air within the instrumentcasing;

The recorder is also effective to provide reference marks in, the middleof the chart so that thetimes of any noteworthy values of the recordedvariables may be, later identified, e. g., the time of startinga trip orof using a radio in the, craft. The operator merely presses a referencemarker button to, cause the mark to be made. This button may be eitherat the recorder or at a distancesince it actuates a switch whichcontrols a solenoid which in turn moves the marker, against a spring,into operative position. This switch may also be operated automatically.

While the recording is intermittent, it is preferably at such a highrate, once per second, e. g., that the records of each value normallyappear as continuous. lines.

The-instrumentissuppliedwith 26 volt, 400 cycle power. It containstwolights for the chart-andthe four indicating; scales, a: manuallyoperated light switch being furnished for, turning the lights on andoff. A section of the chart is always visible which shows the operatorat all timeswhat has happened in the preceding fifteen minutes.

Two electrical motors are operated from the power supply when a motorswitch isturned on. Onemotor merely turns an eccentricweight to cause aslight vibration which substantially eliminates errors of themeasurements due to mechanical or coulomb friction. The other motordrives the chart and a platen for tapping the chart and a fourcolorribbon against four recording pins. Since the frequency of the powersupply on a craft is occasionally not of sufiicient accuracy for timingthe chart, the chartoperating motor used is of the induction type whichcan slip considerably without stalling and is provided with a brake toregulate its speed, the vibratormotor being the the same sort.

The brake is actuated by the difference between a speed that isproportional to the operating motor speed and that of an escapementwhich is driven by a spring which is wound by the motor, ascrew-differential mechanism being used for this purpose. This compactlight-weight regulated motor solves the problem of operating therecorder at a substantially constant speed as is required for subsequentinterpretation of the records.

The chart-operating mechanism is geared to the speedregulated motor sothat the timing roll turns the chart at the desired speed of twelveinches per hour. The chart passes into guides which cause it to bere-rolled, two re-roll O rollers being turned at a peripheral speed ofapproximately twenty-four inches per hour to ensure a tight roll whichis convenient for filing. A tear-off strip with serrated teeth isprovided. This chart-handling arrangement is very light and eliminatesthe usual detachable heavy re-roll roller that occasionally is lost ormislaid when needed.

The ribbon is also driven by the regulated motor which turns two drivinggears, one of which is engaged at a time with its respective spool, asplined connection being used for the shaft that carries the two drivinggears. The drive is shifted from one spool to the other by afour-pronged cam which actuates a reversing lever that moves thedriving-gear shaft endwise on a reversal. This cam is also driven by theregulated motor so that a reversal occurs every one and one-half hours.Friction clutches are provided between the driven gears and the spoolsso that the ribbon can neither be damaged nor stall the recorder in casethe ribbon is not reversed when it first reaches the end of its travelfrom one spool to the other.

To ensure the use of the entire surface of the ribbon,a two-lobed cam isprovided to slowly oscillate the ribbon vertically. This cam is attachedto a 40-tooth ratchet which is pawl-actuated by the reversing lever oneach complete reversing cycle, a complete vertical oscillation of theribbonoccurring every thirty hours.

The printing platen is actuated by a two-lobed cam driven by theregulated motor. Theplaten is spring-biased toward the paper but pushedaway once a second by a lever which is operated by the cam. When the endof the lever drops off the end of a lobe of the cam, the platen tapsthev chart and ribbon against the several recording pins, marginal,markers and the reference marker when the latter.

is in its marking position. a V

A platen lock-out detentlever is locatedby the camoperated lever to holdthe platen well clear of theribbon so that the chart can be readily.inserted and also for cold-starting, at which time the chart-drivegearing may be turned by hand until its motor can carry, the load.Adjusting screws for the platen stroke governthe strengthof the recordedlines on the chart.

Each synchro receiver operates through an angle of 330, or 165 each sideof its electrical zero. Each receiver has itsrespective pulley ofslightly less .than 4.

inches diameter. A thin multi-filament cellulose acetate cord isconnected with the pulley and its indicating and marking pin. The cordpasses from a groove in the drive pulley to the marking pin and thenaround an idler pulley at the opposite end of its scale, the cordreturning toanother idler pulley at the drive pulley end of the scale,and finally to another groove in the drive pulley, the cord being 'onthe opposite side from that in the first-named groove and secured undernegligibly dn've pulley.

slight tension to the This arrangement enables the rotary movement ofthe receiver to be translated into longitudinal movement of theindicating and marking pin along its scale with a minimum of frictionand with free operation over a very wide range of temperature. Thevibrator-motor cooperates in obtaining this result by substantiallyeliminating errors due to mechanical friction. The platen is normallyaway from the paper and ribbon so that light springs on the back of thescales normally force the ribbon away from the pins, thus leaving thepins free to assume their correct positions.

A border marker is attached to one of the scales at each end to indicatetrue range limits on the chart so that effects of changes in width ofthe paper chart due to changes H in relative humidity and temperaturecan be eliminated.

In the middle of the chart is a reference marker which is actuatedagainst a spring by a solenoid to come into marking position when thesolenoid is energized. The reference marker records the times ofnoteworthy events such as the start of a trip or flight or the entryinto a cloud.

The electrical system for operating the instrument when a motor switchis turned on includes a transformer producing the necessary voltages,15, 40 and volts from the 26 v., 400 cycle supply. As soon as the motorswitch is turned on, the vibrator motor and the regulated motor bothstart instantly. The rotor coils of each of the four synchro receiversare energized and two of their three field coils shorted so that eachsynchro receiver is immediately brought to its electrical zero position.

After a 15-second warm-up delay, a duo-diode tube energizes the relaycoil to operate the relay to connect each of the synchro receivers toits respective transmitter with the result that the receiver then movesits index and pin to a position corresponding with the value beingtransmitted.

This centering and delay feature is necessary to eliminate a tendencywhich otherwise exists for the synchro receiver to go to its endposition when the starting position' of the receiver happens to be nearone end of the scale and its transmitter happens to be at the other whenthe telemetering circuit is first closed. Without this delay feature, itwould be necessary to limit the total travel of the synchros to lessthan which would result in a considerable loss of accuracy.

Each of the functionally related groups of elements is separatelymounted as a readily detachable interchangeable sub-assembly tofacilitate calibration or inspection and maintenance.

From the foregoing resume, it is manifest that a simple, lightweight,accurate, multipoint, indicatorrecorder has been provided, by means ofwhich the afore mentioned objects have been attained.

Referring now to the drawings for a more detailed description and moreparticularly to Figure 1 thereof, the present invention is shown ascomprising an instrument casing 30 provided with a cover 31 which in itsassembled condition hooks on at the bottom of the casing and is securedto the top thereof by way of suitable latches 32. Cover 31, on the otherhand, is provided with a Window 34 which exposes to view scales 33arranged near the bottom of the window as well as a section of a stripchart 35 containing recorded values of the functions being measured fora predetermined time interval.

Each of the scales 33 is provided with an index 36 for indicating theinstantaneous measured value of each variable, the values beingrespectively recorded as represented by the lines 37 on the chart.Marginal lines 38 (only one being visible in Figure l) are recordedcontinuously to provide a reference independent of temperature orhumidity effects on the chart sheet while a reference mark 39, centrallyshown on the chart, is recorded when the operator presses referencemarker button 41. A suitable mounting bracket (not shown) is connectedwith the casing 30 by resilient shock mounts by means of which theinstrument may be detachably secured to the craft.

The major components of the novel instrumentof the present invention areshown in Figures 2-7; inclusive, wherein the cover and easing have beenremoved. For example, the chart feed'roll'44 (Figure 6) is arranged atthe front of the instrument, below indicating scales 33.

A driving motor 45 is arranged, as shown in Figures 2 ribbon 49 (Figures4 and 6) carried by a pairof spaced parallel spools 51 which are drivenfrom motor 45 through gearing 46 in one direction or another relative tothe strip chart by means of a horizontal cross-shaft 52 (Figure713). Inorder to effect periodic reversal of the ribbon, a cam 53 (see Figures 2and is provided which actuates a pivoted lever 54 (Figure 3) and, at asubstantially lower rate, the entire ribbon mechanism generallydesignated withthe reference character 55 in Figure 3.

Arranged at the top and front of the instrument, as shown in Figure 6,is a timing chart drive roller 56 which is also driven from gearing. 46.To the rear of the roller is a tear-off bar or strip 57, re-roll springclipsor guides 58 and a pair of re-rollers 59 whose speed is designed tobe higher than that of used portion of the strip chart.

A vibrator motor 61.is mounted on framework 48, as shown in Figure 3,and drives a mass 60 whereby mechanical friction imposed upon theindicatingindices or marker pins is overcome. framework vibrator motor.Chassis 63 of Figure 7 defines a support for the electrical zeroingmeans comprising the relay,

tube, etc,, generally designated with the reference ,charac-.

ter 64 in Figure 22 Above chassis 63 in the rear ofthe instrument is atorquetube 65 for the ribbon mechanism while behind the scales 33 andmarking pins are the ribbon 49 and paper chart 35.

As better shown in Figure 6, a platen 67 is normally biased toward urgedaway fromthe chart by means of levers 69 depending from a crossshaft 71one end of which is provided. with alevcr 72 (Figure 2) which is,operated once a.

second by way of a timing cam 73 provided that lever 72 is not at thattime held out of operation by a lock-out detentlever 74. (see Figure 4).A finger 70 attachedto Constant speed regulator Inasmuch asthe drivingmotor 45 is subject to speed variation with fluctuations in the powersupply and since it is desirable tomaintain the operating portions ofthe,

instrument at a substantially constant speed, themotor is connected bygearing 46 with a spur gear 3% (Figs. 8 and 9) which is attached to a abrake disc 32 which rotates between a fixed washer 83 and'a floatingwasher 84which is restrained against rotation by a fined pin 85. Washer84, moreover, is urged toward disc 82 by a spring86 which is governed bya brake lever 87 pivoted atone BHClrOIJ a fixed pin 88, thel otherendof-the=brake lever-being governed by. the; ac-

drive roller 56 to tightly wind the Also supported. by theareconventional capacitors. 62 for motors 45- and 61, the capacitors beingarrangcd on eachside of the the chart by means of springs 68, andshaft31, the latter bearing;

cumulated or integrated difference of the speed of shaft 81 from thedesired constant speed.

Also actuated by gearing 46, but at a lower speed, is an idler pinion 89which is connected with a gear 91 which is secured to a shaft 92. A gear93 is connected with a constant speed escapement mechanism and has itshub 94 threaded internally for cooperation with the threads 95 providedon shaft 92 so that any difference in the'relative speed of gears 91 and93 is reflected by an axial movement of gear 93 relative to shaft 92.Gear hub 94 is provided with a circumferential groove 96 which supportsone end of brake lever 87 to provide brake actuation to slow motor .5until it runs at the desired speed. A torsional spring 97 connects gears91 and 93 to permit rotation of gear 93 relative to gear 91, gear 93being driven by the spring.

As more clearly shown in Figures 11 and 12, gear 93 drives a pinion 93to which is affixed an escapement ratchet wheel 99. Two escapement pins101 are oscillatably driven by the ratchet wheel and are mounted on arock lever 102 which has a notch 103 that cooperates with an eccentricpin 104011 a balance wheel 105 which is timed by a spring 196. Balancewheel M5 and spring 106 are connected with a shaft it)? which isprovided with a notch 108 that cooperates with another lever 1:29 thatmoves angularly with lever 1&2 to lock the rock lever 102 and escapementwheel 99 except at intervals timed bythe balance wheel and spring f,levers 162 and 169 being secured together and to their common shaft 111.

When motor driven shaft 92 rotates too rapidly, its thread 95 forcesgear hub 94 away from gear 91 to move brake lever 87 in a direction toexert pressure on spring 86 and on high speed brake disc 82 so thatmotor 45 is gradually slowed down to the speed that corresponds withthat of escapement controlled gear 93. By this provision a novelandeificient lightweight drive has been provided which is substantiallyindependent of frequency and voltage variations of the power supply.

Chart operation As more-clearly shown in Figure 2, th chart feed roll isslipped on a stud 112 which is fired in framework 48. A friction drag isprovided at the opposi e end of the roll comprising a spring 113 actingagainst a grooved hub 114 which turns with the chart feed roll, the hubbeing rotatably mounted on a lever M5 which is pivotally-mounted on apin 116 which is attached to the framework 48. Lever is aiso connectedwith the framework'by tension spring 137 (Figure 6) which biases lever115 against a stop portion fli of the framework. As shown in Figured,-screw adjustment 119 is provided on the framework to insure horizontalalignment of the paper feed roll.

Thestrip chart is threaded upwardly over an idler roller 121 (Figure 6)which is shorter than the width of the paper and centrally locatedthereof and between ribbon 4-9 and platen 67 upwardly to chart driveroller 56, the two-ends of which are provided with a plurality of chartdriving pins 122. Chart drive roller 56 is supported on a shaft123'which carries a hub i24- fixed near one end thereof andwhichsupports thereon a plurality of spacer hubs 125 (Figure 2), theshaft being driven at aconstant speed by gearing 46 which includes anirreversible slip clutch generally designated with the referencecharacter 76. This clutch permits the chart drive rolier to be turned inone direction only, the drive being overpowered bymeans of a knob75'arranged at the opposite end of the roller.

Chart drive roller shaft 123 is connected by gearing 46 with a hub 127(Fig. 15) or" the slip clutch, springs 128 being connected to the clutchgear to coact with notches 129 formed in the face of hub 12'] adjacentthe gear-so that the springs exert a frictional effect during part'of arevolution-and at the same time act as pawls coacting with notches-orratchet teeth 129. Gearing 131 (Fig. 2) connects shaft 123 with twofriction rollers 59 so that, when shaft 123 is turned either manually orby motor 45, both roller 56 and re-rollers 59 are operated at the sametime. Spring guides or clips 53 (Figure 6), secured to the framework bylevers 139, guide and hold the chart in a roll while it is beingre-rolled by rollers 59.

The opposite end of roller 56 is provided with a hub 133 having aplurality of chart engaging pins 122 thereon for driving the charttogether with hub 124, hub 133 being free to move axially relative toshaft 123 with changes in the width of the chart but is restrainedagainst turning by pin 134 which is fixed to shaft 123 and coacts with aslot 132 in hub 133.

Ribbon drive The complete mechanism for driving the ribbon together withits automatic reversing means is illustrated in Figures 2, 3, 5, 7 and13 wherein the ribbon driving shaft 52 is shown operated from gearing 46by virtue of a slotted hub and pin drive 135. Pinion bevel gears 136 and137 are fixed to shaft 52 and respectively engage related bevel gears138 and 139 for reversibly feeding the ribbon. Each of gears 138 and 139is attached to the upper end of its respective shaft 141 which hasmounted on its lower end a slip clutch 142 that carries depending pins143. Each of the ribbon spools 51 is mounted on a vertical shaft 144 inwhich, at its upper end, is fixed the horizontal pin 145 in the path ofpins 143 so that the latter angularly drive shaft 144. With the aboveclutch arrangement, the first complete traverse and reversal of theribbon, put the ribbon into normal operation without further slipping ofeither of the clutches.

Each spool 51, moreover, is rotatably mounted so that its shaft'turnsfreely in a yoke lever 146 which is fixed to the torque tube 65 whichextends horizontally across the rear of the instrument and having itsends pivotally and detachably connected with the framework. One end oftube 65 slips over a stud 147 (Fig. 7) which is fixed in the frameworkwhile the other end is snapped over a conical center 148 which ispressed toward the tube by a spring 149 whose opposite end abuts againstthe framework. Since both yoke levers 146 are attached to tube 65, thespools 51 move together in a vertical direction.

The chart drive roller shaft 123 is also connected by gearing 131 with agear 151 whose hub 152 carries an irreversible helical-spring clutch153. Also rotatably mounted on hub 152 is the four lobed reversing cam53 which has alternate lobes 155 pointing in opposite directions.

The ribbon reversing lever 54 has pivotally mounted thereon near itsfree end a roller 156 which is moved in a direction generally parallelto the axis of hub 152 by the lobes 155, being retained in its newposition by the then adjacent segment portion 157 of cam 153. Theresultant operation is that a steady rotation of gear 151 and cam 53produce reciprocating motion of roller 156 and reversing lever 54 onceevery one and one half hours when cam 53 rotates once every six hours.

The ribbon reversing lever 54 also carries, near its free end, a springpawl 158 which engages a ratchet wheel 159 that is provided with a twolobed fiat cam 160 on its opposite side. Since ratchet wheel 159 has 40teeth, earn 160 operates a ribbon oscillating pin 161 to make oneoscillation every thiry hours. Pin 161 is slidably mounted in theframework to reciprocate vertically its lower end being pressed upwardlyby a bolt 162 which is fastened to one of the yoke levers 146, the otherof the levers being biased upwardly by a spring 170 as shown in Figure13.

The resulting operation is that both yoke-levers 146 and their spools 51rise and fall together through a complete oscillation in every thirtyhours, each spool 51 being meanwhile driven by gears 138 or 139 and itsthen related gear 136 or 137. The vertical-stroke or oscillation ofribbon 49 is slightly less than one'quarter of the total width of theribbon where a four color ribbon is used thus insuring that practicallyall of the ribbon is used up evenly.

The outer end of each yoke lever 146 carries a vertical roller 163(Figures 3 and 13) which isrotatably mounted on its related lever whileguiding members 164 are provided for the ribbon adjacent each roller 163and attached to the yoke levers through which the ribbon may be threadedso that it will positively move vertically with the yoke levers, aguiding portion thereby being provided at both edges of the ribbon onboth sides of each roller 163. Each spool 51 at its bottom is providedwith braking means so that ribbon 49 is kept taut between the two guiderollers 163 and guide members 164.

Platen operation As pointed out hereinabove, platen 67 is actuated bylever 72 which, when released by detent lever 74, is urged by means ofsprings 58 toward cam 73 and drops quickly from the tip to the root ofthe tooth of cam 73 as the end of lever 72 passes the tip of the tooth.Cam 73 is preferably made of chrome-plated hardened steel and has asmoothly polished surface. The end of lever 72 is made of hardened steelwhich is also chrome-plated and provided with an oil felt wiper 165, aconstruction which ensures long life of this rapidly working part.

The platen lock-out detent lever 74 is pivotally mounted on theframework 48 and urged into contact with a cooperating portion of lever72 by spring 166 whose lower end is attached to lever 72 and whose upperend is connected with the adjustable eccentric pin 167. The arrangementis such that, when the lever 74 holds lever 72 away from cam 73, therotation of cam 73 does not cause operation of the platen 67 but holdsthe latter a greater-thannormal distance away from the chart 35.

The lower end of lever 72 is connected to cross-shaft 71 which carriesthe two depending levers 69 which push against the adjustable screws 168(see Fig. 14) to move the platen 67 back against the action of itssprings 68.

Platen 67 is connected to two parallel pins 169 which slide in guideholes in framework 48. The result is that the platen 67, when the end oflever 72 slides off the end of a tooth of cam 73, is moved sharplytoward the chart 35 by springs 68 to make a legible impression on chart35 of each of the marking pins 66 through its respective colored portionof the ribbon 49. The back of one of the scales 33 is provided with themargin marking pins 171 which make two lines 38 just ten inches, e. g.,apart so that the expansion or contraction of the paper due to relativehumidity may be corrected for.

A reference marking pin 172 (see Figs. 17 and 21) is normally biased toan inoperative position, i. e., above the platen 67, by spring 173, oneend of which is fixed to the adjacent scale 33. A solenoid 174, whenenergized, operates its plunger 174' to move the reference marker pin172 to an operative position against the bias of spring 173. Solenoid174 is energized by a switch (not shown) which is operated by referencemarker button 41 (see Fig. 1) which is pressed by the operator to recordthe time of some noteworthy event such as the start of a trip of a craftor its entry into a cloud or fog.

Synchi'o marker actuation F or a detailed description of the marker orindex operation by the synchronous repeaters reference is made toFigures 2, 17-20. Each synchro receiver 175 has a rotatable shaft 176carrying a pulley 177 of slightly less than 4'inch diameter. Ears 178 oneach pulley 177 engage a respective stop 180 attached to framework 48 tolimit the angular movement of each pulley to substantially 330.

" an idler pulley 183. Attached to the straight portion of the cord isthe indicating and marking pin 66, the inner end of the pin beingrounded to make an impression through ribbon 49 on chart 35 when thelatteris tapped by the platen 6,7.

Normally, the platen is out of'engagement with the chart 35 and theribbon 49 is then pressed away from the marking end of pins 66 byweakstrip springs 184 .so that each pin 66 can move freely with itscord182. The cord from idler pulley 183 returns across the chart infront of the scales to idler pulley 183' and thence to the groove 181 inthe pulley 177 to which it is fastened under extremely slight tension.Idler pulleys 183, 183', pulley 177 and ribbon 49 are disposed insubstantially the same plane to provide for using a plurality of ribbonsside by side to indicate a plurality of variables on a single chart.

The vibrator motor 61 rotates its eccentric weight 60 at high speed whenthe system is operating so that there is a minimum of error due tomechanical friction in the instmment.

Electrical system Refer to Figure 22 which shows the diagram of theelectrical system. The lights 188 are connected with the supply line 185by the light switch 189. A supply line 185 is connected to the 26-volttap of the auto-transformer 186 by closing the motor switch 187. Inseries with motor switch 187 is fuse 191, which is connected to motors45 and 61 in parallel, each motor having its own capacitor 62, with theresult that closing the motor switch 187 starts both motors.

The relay 195 has armature 190 spring-biased away from its stationarycore with eight contacts 197 closed and single contact 193 open when thecoil is de-energized, as shown on Figure 22.

Closing the motor switch 187 energizes the 40-volt armature coil 1.92 atthe synchro-receiver 175. Since telemetering contact circuit switch 193is open when the motor switch 187 is first closed, this 40-volt A. C.potential is not then impressed upon armature coil 194 at the synchrotransmitter. At this time, i. e., when first starting up, the coil ofrelay 195 is not yet energized, with the result that the relay switch193 is still open so that the 40- volt potential is not yet supplied tothe telemetering circuit connecting the synchro transmitters 190 withthe synchro receivers 175. Incidentally, the disconnect 196 isconveniently located on the instrument case 30. At this time, relaycontacts 197 are still closed, to short two of the field coils of thesynchro receiver 175 and putting both of these in series with the 15volt A. C. potential from auto-transformer 186. The result is that thereceiver armature coil 192 automatically comes to its electrical zeroposition at this time.

In the meantime, the duo-diode tube 198 is warming up since it isconnected, by closing the motor switch 187, with the 26 volt supply 185.After about 15 seconds, during which the armature 192 of each synchroreceiver 175 has come to its electrical zero position, the duo-diodetube 198 acts to energize the coil of the relay 195 to then operate therelay armature 190 to close switch 193 and open all contacts 197. Whenrelay contacts 197 are opened and relay contact 193 is closed, thereceiver armature 192 immediately moves to a position corresponding withthat of armature 194 of the synchro transmitter 190, thus putting theinstrument into complete operation.

Switch 199 is operated by the reference marker 41 to energize the coilof solenoid 174. Alternatively, this solenoid 174- may be energized byclosing switch 200 which is located remotely of the instrument.

It is apparent that a simple electrical system has been provided whichis well suited to the needs of any craft having the usual A. C. powersupply.

In the claims, a synchro used for telemetering includes an armaturehaving a single phase Winding energized from an A. C. supply, and awinding equivalent to two or more coils, preferably three for presentpurposes, in inductive relation with the armature coil and connectedwith telemetering circuits.

Although but one embodiment of the present invention has beenillustrated and described in detail, it is to be expressly understoodthat the invention, is not limited thereto. Various changes in thedesign and arrangement of the parts can be made without departing fromthe spirit and scope of the invention and the same will now beunderstood by those skilled in the art. For example, an equivalent ofthe duo-diode would be any other timedelay means for energizing therelay coil at a suit able interval after the receiver had been energizedto thus allow its armature to be electrically centered so that, uponstarting up, the receiver would not go to its limits but wouldimmediately take up a position corresponding to that of its transmitter.For a definition of the limits of the invention, reference will be hadprimarily to the appended claims.

We claim:

I. In combination with a recording instrument having a marker linearlymovable across a chart in response to the value of a variable beingmeasured together with means for actuating said marker as a function ofthe variable being measured, a platen for urging said chart against saidmarker, a removable casing for said instrument, means adapted foroperation when said casing has been removed from said instrument forholding said platen in an inoperable position, and means carried by saidcasing and operable when said instrument has been placed in said casingfor releasing said platen holding means.

2. A recording instrument for a flat traveling chart having a markingface, comprising a linear guide extending transversely to, along saidface of and adjacent to the chart, means for marking the chart,including a marking element traveling along the guide and said face ofthe chart, a marking ribbon extending between the marking element andthe chart along the path of the marking element, a platen movablymounted on the opposite side of the chart from the ribbon, yieldablemeans biasing the platen toward the chart, means for holding the platenout of marking engagement with the chart against the action of theyieldable means, and means for periodically actuating the holding meansand thereby bringing the platen into marking engagement with the chartby the action of the yieldable means.

3. A recording instrument for recording a plurality of variables on aflat traveling chart having a marking face, comprising a plurality oflinear parallel adjacent guides extending transversely to the chart inmarking relation thereto, a plurality of marking elements each mountedfor travel along a guide and normally out of marking relation to thechart, a marking ribbon extending transversely to the chart between thepaths of said marking elements and the chart, means for positioning eachmarking element in accordance with the value of a variable, and meansfor bringing all of said marking elements simultaneously into markingposition in engagement with said ribbon and chart to mark the positionsof said indicators on the chart, comprising a platen movably mounted inalignment with the paths of all of the marking elements on the oppositeside of the chart, and means for periodically shifting the platentowards said elements and thereby bringing the chart, ribbon and markingelements simultaneously into marking position.

4. A recording instrument for a fiat traveling chart, comprising amarking element mounted for travel in a path transverse to and spacedfrom the chart, means for moving the marking element along said path, amarking ribbon extending between the marking element path and the chart,means for periodically bringing the marking element into markingengagement with the ribbon and chart, and means for biasing the ribbonaway from the marking element during intervals between such engagements,whereby the marking element is free from frictional contact with theribbon during movement.

(References on following page) References Cited in the file of thispatent UNITED STATES PATENTS 12 Urfcr May 14, 1935 Lyman June 7, 1938Goddard June 28, 1949 FOREIGN PATENTS Great Britain May 25, 1936

